Mhmm - i am not a ship-construction- or electric-expert - but all these new electric double-end-ferries (also in Norway, Sweden etc.) - the both screws / propulsion-systems are always placed under both ends of the ships.
So mainly you need only the (today so small like a big bucket only) electric engine(s) (and converter etc.) and the connections from the batteries to the engine(s) and from the engines to the screws.
If we now think that the batteries will be stronger and smaller every year in future - would it then make sense to place the batteries anywhere down under very deep inside the ship ?
There is no big engine-room anymore needed and also no fuel-tanks.
But if the batteries would be placed where it is easy to change them against new better stronger in the future - it would save a lot of costs.
Just if we think that these new ferries will be in operation 20, 25 or 30 years - but i am 100% sure that no battery will work so long.
(A)
https://cdn.offshorewind.biz/wp-con...4150516/FST_img_BatteryFerry_ENG-1024x690.jpg
So here in this picture (A) the big batteries are placed under the deck - but think 10 years further - i am 100 % sure that in 2034 maybe only 15 or 20% of this big space is needed then for the same battery-power and range.
So if the batteries would be placed today at the sides on both ends of a double-end-ferry they could be much more easy changed later - and maybe then also place for 2 cars (or motorbikes) more onboard.
But with underground-placed-batteries - much more complicated to change it later and then you have big empty unused space there.
(B)
https://www.marinelog.com/wp-content/uploads/2021/11/Ferry-Design.png
Here in this picture (B) the batteries are ON the sides of the car-deck - i would always prefer such an solution now if i would order now any new 100% electric ferries.
Short way for charging at docking and short ways from the batteries to engines, converter, screws etc. .
And a lot of things can be easy checked / repaired / changed without to step down anywhere under the deck.